1. Field of the Invention
The present invention relates to an electron emission device and a electron emission display device using the same.
2. Description of Related Art
In field electron emission display apparatuses, an FED (Field Emission Display) is known as a planar emission display device equipped with an array of cold-cathode electron emission sources which do not require cathode heating. The emission principle of, for example, an FED using a spindt type cold cathode is as follows: Its emission principle is like a CRT (Cathode Ray Tube), although this FED has a cathode array different from that of a CRT, that is, electrons are drawn into a vacuum space by means of a gate electrode spaced apart from the cathode, and the electrons are made to impinge upon the fluorescent substance that is coated on a transparent anode, thereby causing light emission.
This field emission source, however, faces a problem of low production yield because the manufacture of the minute spindt type cold cathode is complex and involves many steps.
There also exists an electron emission device with a metal-insulator-metal (MIM) structure as a planar electron source. This electron emission device with a MIM structure has an Al layer as a cathode, an Al.sub.2 O.sub.3 insulator layer of about 10 nm in film thickness and an Au layer, as an anode, of about 10 nm in film thickness formed in order on the substrate. With this device placed under an opposing electrode in vacuum, when a voltage is applied between the underlying Al layer and the overlying Au layer and an acceleration voltage is applied to the opposing electrode, some of electrons leap out of the overlying Au layer and reach the opposing electrode. Even the electron emission device with the MIM structure does not yet provide a sufficient amount of emitted electrons.
To improve this property of emission, it is considered that there is a necessity to make the Al.sub.2 O.sub.3 insulator layer thinner by about several nanometers and make the quality of the membranous Al.sub.2 O.sub.3 insulator layer and the interface between the Al.sub.2 O.sub.3 insulator layer and the overlying Au layer more uniform.
To provide a thinner and more uniform insulator layer, for example, an attempt has been made to control the formation current by using an anodization thereby to improve the electron emission characteristic, as in the invention described in Japanese Patent Application kokai No. Hei 7-65710.
However, even an electron emission device with a MIM structure which is manufactured by this method ensures an emission current of about 1.times.10.sup.-5 A/cm.sup.2 and an electron emission efficiency of about 1.times.10.sup.-3.